1. Field of the Invention
The present invention relates to a droplet discharge head and a manufacturing method thereof, and more specifically to a structure for a piezoelectrically driven droplet discharge head for varying the volume of the pressure chamber using a laminated piezoelectric body to discharge droplets from a nozzle, and a manufacturing method thereof.
2. Description of the Related Art
Japanese Patent Application Publication No. 8-011304 discloses an inkjet head using a laminated piezoelectric body, which is formed by alternately laminating piezoelectric material and electrodes. The inkjet head has a structure in which a laminated piezoelectric body has two or more rows of pectinate shapes formed by half-cut grooves, and the position of each divided tip thereof is joined in accordance with the position of the pressure chamber. The inkjet head also has a structure in which a laminated piezoelectric body partitioned by grooves is arrayed in the form of a matrix, and a higher density of nozzles in a single row is achieved with two rows of piezoelectric elements. It is doubtful that this structure can be constructed with three or more rows of piezoelectric elements, and it is possible that a structure in which a nozzle row with a single color is constructed with two rows of piezoelectric elements is envisioned in the publication.
Moreover, in Japanese Patent Application Publication No. 8-011304, the pectinate portions partitioned in the form of teeth of a comb by the groves are all active portions (portions by which pressure is generated for varying the volumes of the pressure chambers), and there are no partition walls corresponding to the shape of the pressure chambers, so there is concern that undesirable crosstalk may occur when an adjacent pressure chamber is driven.
Furthermore, when the pectinate laminated piezoelectric body disclosed in Japanese Patent Application Publication No. 8-011304 is joined to a long head, the mechanical strength of the piezoelectric body is low with respect to stress produced by bonding or heat during the production, or with respect to warping produced in the entire head plate by its own weight, and there is a possibility that the piezoelectric element may be damaged when partition grooves are formed along the direction orthogonal to the lengthwise direction of the head.
Japanese Patent Application Publication No. 2003-226007 proposes an actuator unit with a structure in which a plurality of layers of piezoelectric sheets having a size sufficient to span all of the pressure chambers are laminated, and in which internal electrodes are separated and individually formed for each pressure chamber in an inkjet head in which a plurality of pressure chambers are arrayed in two dimensions. However, this laminated structure has the drawback in that a sizable displacement cannot be obtained because the piezoelectric elements corresponding to the pressure chambers are not mechanically segmented, and there is also adjacent crosstalk. Moreover, since electrode patterns are used in which individual electrodes corresponding to each pressure chamber are preformed with the same pattern as the array pattern of the pressure chambers, there is the drawback in that it is difficult to control the position displacement produced by shrinkage (about 30%) when the piezoelectric element is made by calcining.